Chile
Veronicellid phylogeny
17-08-2010 11:39
Veronicellidae are
large, tropical slugs, which are widespread in the
Neotropics. In South America 16 genera are known to
occur, and many species are recorded as agricultural
pests or intermediate hosts for nematodes, causing
public health risks.
In the southern part of the continent, six species of the genus Phyllocaulis occur. Recently, a phylogenetic study explored the relationships between these species (Gomes et al, 2010).
Most of the species have a sympatric occurrence in part of their distributional range.
The results showed that the different species of Phyllocaulis are in mutually exclusive and well-supported clades. Interestingly, a study of the divergent times showed that the vicariant species P. gayi (Chile) and P. soleiformis (Argentina) had their common ancestor during Pleistocene times (~ 0.6 Ma). Since this timing is after the final upheaval of the Andes, the distribution is explained by cross-Andean dispersal and subsequent speciation.
Reference:
Gomes, S.R., Britto da Silva, F., Mendes, I.L., Thomé, J.W., Bonatto, S.L., 2010. Molecular phylogeny of the South American land slug Phyllocaulis (Mollusca, Soleolifera, Veronicellidae). - Zoologica Scripta 39: 177-186.
In the southern part of the continent, six species of the genus Phyllocaulis occur. Recently, a phylogenetic study explored the relationships between these species (Gomes et al, 2010).
Most of the species have a sympatric occurrence in part of their distributional range.
The results showed that the different species of Phyllocaulis are in mutually exclusive and well-supported clades. Interestingly, a study of the divergent times showed that the vicariant species P. gayi (Chile) and P. soleiformis (Argentina) had their common ancestor during Pleistocene times (~ 0.6 Ma). Since this timing is after the final upheaval of the Andes, the distribution is explained by cross-Andean dispersal and subsequent speciation.
Reference:
Gomes, S.R., Britto da Silva, F., Mendes, I.L., Thomé, J.W., Bonatto, S.L., 2010. Molecular phylogeny of the South American land slug Phyllocaulis (Mollusca, Soleolifera, Veronicellidae). - Zoologica Scripta 39: 177-186.
Bostryx from Chile
28-06-2010 13:29
Dulack Richards sent me
some shells for identification, mostly from Peru. One
lot was included from Chile that proved to be very a
interesting Bostryx
species. Firstly, many
Chilean Bostryx
species are poorly
known (see also here)
and every accurate record is greatly welcomed.
Secondly, one shell was somewhat damaged and nicely
showed some internal detail.
These shells are probably B. holostoma (Pfeiffer, 1846), described from Cobija. The specimens collected by Richards were found north of Caldera, under rocks near the sea. Although not explicitly stated on the label, this sounds like a locality with lomas vegetation.
Rehder (1945) already stated that this species “has a short but strong columellar lamella within the last whorl”. The shell pictured above shows the same characteristic.
Reference:
Rehder, H.A., 1945. The Chilean species of the molluscan genus Peronaeus (Bulimulidae) - Revista Chilena de Historia Natural 48: 102-107.
Update
Meanwhile I ascertained that these specimens are B. leucostictus (Philippi, 1856), a closely related species described from Paposo.
These shells are probably B. holostoma (Pfeiffer, 1846), described from Cobija. The specimens collected by Richards were found north of Caldera, under rocks near the sea. Although not explicitly stated on the label, this sounds like a locality with lomas vegetation.
Rehder (1945) already stated that this species “has a short but strong columellar lamella within the last whorl”. The shell pictured above shows the same characteristic.
Reference:
Rehder, H.A., 1945. The Chilean species of the molluscan genus Peronaeus (Bulimulidae) - Revista Chilena de Historia Natural 48: 102-107.
Update
Meanwhile I ascertained that these specimens are B. leucostictus (Philippi, 1856), a closely related species described from Paposo.
Orthalicid radulae (3): Plectostylus
10-12-2009 20:37
Continued from
last
month,
today the radula of Plectostylus
coquimbensis (Broderip, 1832) from
Chile,
Coquimbo. Radula formula: C/1 + L16/1 + M56/3.
From top to bottom, left to right: overview, showing half row; C+L1; teeth 18 (M2); teeth 56-57 (M40-41); teeth 30-31 (M14-15); teeth 44-53 (M28-37); teeth 27-34 (M11-18).
From top to bottom, left to right: overview, showing half row; C+L1; teeth 18 (M2); teeth 56-57 (M40-41); teeth 30-31 (M14-15); teeth 44-53 (M28-37); teeth 27-34 (M11-18).
Chilean acavid
02-12-2009 20:13
The family Acavidae is
a rare find in the Neotropics. This family may be
found in the ‘Old World’ in Australia, Seychelles,
Sri Lanka and Madagascar. And in Chile, where the
genus Macrocyclis
occurs with its sole
species M.
peruvianus (Lamarck, 1822).
This large species is up to 60 mm diameter. Although it is commonly known as the largest snail in the Chilean land snail fauna, its anatomy was hitherto unknown. Recently, da Silva & Thomé (2009) unveiled more details on the ecology and anatomy.
It was founds after a hard day of searching, under fallen logs near the vicinity of Lago Azul.
This is another case of Gondwanan distribution at the family level. It would be interesting to see if the affinities are confirmed by molecular evidence.
Reference:
da Silva, L.F. & Thomé, J.W., 2009. Macrocyclis peruvianus (Gastropoda, Acavidae), an endemic land snail from Chile. - Iheringa, Zoologia 99(2): 125-128.
This large species is up to 60 mm diameter. Although it is commonly known as the largest snail in the Chilean land snail fauna, its anatomy was hitherto unknown. Recently, da Silva & Thomé (2009) unveiled more details on the ecology and anatomy.
It was founds after a hard day of searching, under fallen logs near the vicinity of Lago Azul.
This is another case of Gondwanan distribution at the family level. It would be interesting to see if the affinities are confirmed by molecular evidence.
Reference:
da Silva, L.F. & Thomé, J.W., 2009. Macrocyclis peruvianus (Gastropoda, Acavidae), an endemic land snail from Chile. - Iheringa, Zoologia 99(2): 125-128.
Another rare paper
13-11-2009 20:29
In the context of the
recent post on climate
and snails, I received a copy of a very
rare paper, although the author sounded familiar: the geographer
and archeologist Alan Craig. The paper appeared in
the journal "Andean Past" and was published in 1992.
Dealing with land snails in archaeological sites, my interest was raised by the paragraph on thanacocoenosis, or the massive accumulation of shells in certain areas. Referring to the case of Bostryx near Antofagasta, Chile (described here), Craig also mentions the massive occurrence of dead snails on the summit of Cerro Reque near Chiclayo, Peru. This is ascribed as the result of parasitation by a fly.
The observation is made that the cacti of the 'lomas' in Chile are replaced by bromeliads (Tillandsia) more northward in Peru. Craig suggests that aestivating snails on Tillandsia are carried from one 'lomas' area to another when the plants are "tangled in the fleece of guanacos". Interesting suggestion, but pure speculation...
The author clearly has a very limited oversight on the malacological literature, neglecting totally the work of e.g. Haas and Weyrauch on Peruvian snails. His figure 2 pictures "Strophocheilid tree snails" from Río La Leche, Lambayeque; these are probably a Thaumastus species. Also his other identifications are possibly erroneous, his Scutalus looks too small to be correct.
I would say: cobbler, stick to your last.
Reference
Craig, A., 1992. Archaeological occurrences of Andean land snails. - Andean Past 3: 127-135.
Dealing with land snails in archaeological sites, my interest was raised by the paragraph on thanacocoenosis, or the massive accumulation of shells in certain areas. Referring to the case of Bostryx near Antofagasta, Chile (described here), Craig also mentions the massive occurrence of dead snails on the summit of Cerro Reque near Chiclayo, Peru. This is ascribed as the result of parasitation by a fly.
The observation is made that the cacti of the 'lomas' in Chile are replaced by bromeliads (Tillandsia) more northward in Peru. Craig suggests that aestivating snails on Tillandsia are carried from one 'lomas' area to another when the plants are "tangled in the fleece of guanacos". Interesting suggestion, but pure speculation...
The author clearly has a very limited oversight on the malacological literature, neglecting totally the work of e.g. Haas and Weyrauch on Peruvian snails. His figure 2 pictures "Strophocheilid tree snails" from Río La Leche, Lambayeque; these are probably a Thaumastus species. Also his other identifications are possibly erroneous, his Scutalus looks too small to be correct.
I would say: cobbler, stick to your last.
Reference
Craig, A., 1992. Archaeological occurrences of Andean land snails. - Andean Past 3: 127-135.
New Taxa (19): Araucocharopa
02-11-2009 19:44
Recently, several new
taxa have been described from Chile.
Another one is now added by Sergio Miquel and
Francisco Cádiz Lorca. It is a small species
belonging to the Charopidae.
After a careful comparison with other genera from the same family occurring in Chile, Argentina and Brazil, the authors have come to the conclusion that this novelty belongs to a new genus. The name is derived from the area where the species is found.
The new species is named in honour of Carlos Gallardo. Type locality: Chile, XIV Región, Prov. Valdivia, Reserva Costera Valdiviana. Holotype: MNHNCL 6610.
Reference:
Miquel, S.E. & Cádiz Lorca, F.J., 2008. Araucocharopa gallardoi gen. et sp.n. de Charopidae (Mollusca: Gastropoda: Stylommatophora) del sur de Chile. - Revista Museo Argentino Ciencias Naturales, n.s. 10: 329-340.
After a careful comparison with other genera from the same family occurring in Chile, Argentina and Brazil, the authors have come to the conclusion that this novelty belongs to a new genus. The name is derived from the area where the species is found.
The new species is named in honour of Carlos Gallardo. Type locality: Chile, XIV Región, Prov. Valdivia, Reserva Costera Valdiviana. Holotype: MNHNCL 6610.
Reference:
Miquel, S.E. & Cádiz Lorca, F.J., 2008. Araucocharopa gallardoi gen. et sp.n. de Charopidae (Mollusca: Gastropoda: Stylommatophora) del sur de Chile. - Revista Museo Argentino Ciencias Naturales, n.s. 10: 329-340.
New taxa (17): Charopidae
06-08-2009 10:25
In the same issue of the Archiv, a paper was
published by Sergio Miquel and Gary Barker about
punctoid shells. This group is poorly known and only
based on shell morphology.
Three new species are described, all occurring in Chile; one species extends into western Argentina. The first record for the genus Lilloiconcha in Chile, is L. aysensis n.sp. from Prov. Aysen, Puerto Chacabuco (FMNH 312442).
The second taxon, Radiodiscus villarricensis n.sp., was found in Prov. Concepción, Fundo El Manzano (FMNH 312443). Specimens of this species have also found in Argentina, Prov. Neuquén.
Finally, Stephadiscus stuardoi n.sp. is described from Prov. Concepción, Hualpén Botanical Park (MNHNCL 6655). This species is named after Dr. José Stuardo, the well-known Chilean malacologist.
These minute land shells are detritus feeders and may be found in leaf litter. Interestingly, the charopids from this area have close relatives in New Zealand, Australia and New Guinea. Further anatomical and phylogenetic research may shed light on these relationships and on the biogeographical processes behind it.
Reference:
Miquel, S.E. & Barker, G.M., 2009. New Charopidae from Chilean-Argentine Patagonia (Mollusca: Gastropoda: Stylommatophora). - Archiv für Molluskenkunde 138: 53-61.
Three new species are described, all occurring in Chile; one species extends into western Argentina. The first record for the genus Lilloiconcha in Chile, is L. aysensis n.sp. from Prov. Aysen, Puerto Chacabuco (FMNH 312442).
The second taxon, Radiodiscus villarricensis n.sp., was found in Prov. Concepción, Fundo El Manzano (FMNH 312443). Specimens of this species have also found in Argentina, Prov. Neuquén.
Finally, Stephadiscus stuardoi n.sp. is described from Prov. Concepción, Hualpén Botanical Park (MNHNCL 6655). This species is named after Dr. José Stuardo, the well-known Chilean malacologist.
These minute land shells are detritus feeders and may be found in leaf litter. Interestingly, the charopids from this area have close relatives in New Zealand, Australia and New Guinea. Further anatomical and phylogenetic research may shed light on these relationships and on the biogeographical processes behind it.
Reference:
Miquel, S.E. & Barker, G.M., 2009. New Charopidae from Chilean-Argentine Patagonia (Mollusca: Gastropoda: Stylommatophora). - Archiv für Molluskenkunde 138: 53-61.
Photo of the day (49): Plectostylus
19-05-2009 18:59
Imagine that you see a mossy tree stem from some
distance. Would you spot the snail on it? Certainly
if you are so near as where this picture was taken
of
Plectostylus
variegatus
(Pfeiffer, 1842).
This photograph was taken in January 2009 by Ad Hovestadt in Chile, Coquimbo, south of La Serena, Parque Nacional Fray Jorge, in cloud forest.
Thanks Ad!
This photograph was taken in January 2009 by Ad Hovestadt in Chile, Coquimbo, south of La Serena, Parque Nacional Fray Jorge, in cloud forest.
Thanks Ad!
New taxa (10): Araucocharopa
18-03-2009 20:14
Minute snails are the Cinderellas of every
malacofauna. Often hard to find and poorly known.
In the Neotropical family Charopidae doubtless many new species are to be described. Recently such a new species was described, for which also a new genus was erected: Araucocharopa gallardoi Miquel & Cádiz Lorca.
It is perhaps merely coincidental that this novelty is described from Chile, like the species mentioned in this post and this one. The type locality is Chile, XIV Région, provincia de Valdivia, Reserva Costera Valdiviana. The holotype is in the collection of the Natural History Museum in Santiago.
There is a useful discussion included in the paper, describing the relations with several other genera of Charopidae, Helicodiscidae and Endodontidae.
Although the paper has a header indicating it was published in 2008, the authors sent me a PDF named “Miquel-CádizLorca2009” which leads me to believe that it was only just published.
Reference
Miquel, S.E. & Cádiz Lorca, F.J., 2008 [2009]. Araucocharopa gallardoi gen. et sp. n. de Charopidae (Mollusca: Gastropoda: Stylommatophora) del sur de Chile. - Revista Museo Argentino Ciencias Naturales, n.s., 10: 329-340.
In the Neotropical family Charopidae doubtless many new species are to be described. Recently such a new species was described, for which also a new genus was erected: Araucocharopa gallardoi Miquel & Cádiz Lorca.
It is perhaps merely coincidental that this novelty is described from Chile, like the species mentioned in this post and this one. The type locality is Chile, XIV Région, provincia de Valdivia, Reserva Costera Valdiviana. The holotype is in the collection of the Natural History Museum in Santiago.
There is a useful discussion included in the paper, describing the relations with several other genera of Charopidae, Helicodiscidae and Endodontidae.
Although the paper has a header indicating it was published in 2008, the authors sent me a PDF named “Miquel-CádizLorca2009” which leads me to believe that it was only just published.
Reference
Miquel, S.E. & Cádiz Lorca, F.J., 2008 [2009]. Araucocharopa gallardoi gen. et sp. n. de Charopidae (Mollusca: Gastropoda: Stylommatophora) del sur de Chile. - Revista Museo Argentino Ciencias Naturales, n.s., 10: 329-340.
New taxa (7): Chilean Charopidae
10-01-2009 14:31
From the same publication mentioned in
this
post,
a new minute land shell:
Chillius
pyramidalis
(gen.nov., spec.nov.). It was described from the same
type locality: Peninsula de Hualpén (holotype
Universidad Concepción 26777) and belongs to the
family Charopidae.
Reference
Vargas, P. & Stuardo, J., 2007. Dos géneros nuevos de caracoles terrestres (Stylommatophora: Arionacea) de Chile. - Revista Biologia Tropical 55: 693-708.
Reference
Vargas, P. & Stuardo, J., 2007. Dos géneros nuevos de caracoles terrestres (Stylommatophora: Arionacea) de Chile. - Revista Biologia Tropical 55: 693-708.
New taxa (6): Chilean Punctidae
07-01-2009 21:49
Speaking on Chilean land snails recently, I like to
draw attention to a new species (and a new genus)
that was described some years ago by Vargas &
Stuardo,
Pichikadi
hualpensis.
It was described from Chile, VIII Región, Peninsula de Hualpén (holotype Universidad Concepción 26799).
Carl Christensen remarked that it is very similar to Paralaoma servilis (Shuttleworth, 1852), a punctid from New Zealand that is now rapidly spreading into the New World and Europe.
Comparing it to this species, the similarities are indeed striking and the dimensions are the same. However, I’m not a specialist in Punctidae and I will give no final verdict here.
Carl, thanks for the note!
Reference
Vargas, P. & Stuardo, J., 2007. Dos géneros nuevos de caracoles terrestres (Stylommatophora: Arionacea) de Chile. - Revista Biologia Tropical 55: 693-708.
It was described from Chile, VIII Región, Peninsula de Hualpén (holotype Universidad Concepción 26799).
Carl Christensen remarked that it is very similar to Paralaoma servilis (Shuttleworth, 1852), a punctid from New Zealand that is now rapidly spreading into the New World and Europe.
Comparing it to this species, the similarities are indeed striking and the dimensions are the same. However, I’m not a specialist in Punctidae and I will give no final verdict here.
Carl, thanks for the note!
Reference
Vargas, P. & Stuardo, J., 2007. Dos géneros nuevos de caracoles terrestres (Stylommatophora: Arionacea) de Chile. - Revista Biologia Tropical 55: 693-708.
Chilean Orthalicidae (2)
04-01-2009 12:58
Linked to my previous post, I found some pictures of
live snails on Flickr.
The first is a species of Bostryx, found near Coquimbo, Punta de Choros. It is hard to say what species precisely, because only this dorso-lateral view is available. Judging from the shell shape and the records from literature, one possibility is B. rouaulti (Hupe, 1857).
All others are Plectostylus. From the same locality is P. coquimbensis (Broderip, 1832).
The next one is from an unknown locality. It resembles P. variegatus (Pfeiffer, 1842) but, again, with only this information it is hard to be conclusive.
Again, no data on the next picture, but clearly a different species judging from the animal alone; the orange neck-stripe and rim along the foot is characteristic. If I have to make a guess, it could be P. peruvianus (Bruguière, 1789).
This looks like the same species...
Another, clearly distinct species. It looks like the photograph was taken in a more wooded part of the country. Supposing this is a more southern species, possibly P. vagabondiae Brooks, 1936 (?).
And these cristal balls are eggs of an unknown Plectostylus species, ready to hatch.
The first is a species of Bostryx, found near Coquimbo, Punta de Choros. It is hard to say what species precisely, because only this dorso-lateral view is available. Judging from the shell shape and the records from literature, one possibility is B. rouaulti (Hupe, 1857).
All others are Plectostylus. From the same locality is P. coquimbensis (Broderip, 1832).
The next one is from an unknown locality. It resembles P. variegatus (Pfeiffer, 1842) but, again, with only this information it is hard to be conclusive.
Again, no data on the next picture, but clearly a different species judging from the animal alone; the orange neck-stripe and rim along the foot is characteristic. If I have to make a guess, it could be P. peruvianus (Bruguière, 1789).
This looks like the same species...
Another, clearly distinct species. It looks like the photograph was taken in a more wooded part of the country. Supposing this is a more southern species, possibly P. vagabondiae Brooks, 1936 (?).
And these cristal balls are eggs of an unknown Plectostylus species, ready to hatch.
Chilean Orthalicidae (1)
03-01-2009 22:02
Preparing information for a friend who will visit
Chile this month, it strikes me that some years have
past since the last publication on Chilean land
molluscs. Most recently some publications appeared in
the ’80s (Stuardo & Valdovinos, 1985; Stuardo
& Vega, 1985).
The latter publication is a synopsis of the land snails, for which detailed catalogues and group analyses were announced “to be published by parts elsewhere”. A far as I know, only a revision of Plectostylus appeared (Valdovinos & Stuardo, 1988).
As is also the case in other countries, the Orthalicidae are a major element of the Chilean terrestrial malacofauna. 42 taxa are listed, one doubtfully recorded for Chile (belonging to Thaumastus); the others all belong to Bostryx and Plectostylus.
While the latter genus has been largely revised, Bostryx remains quite ‘messy’ with 29 taxa. All species occur in northern Chile and seem to flourish in the desertic coastal area. An overview of the Chilean Orthalicidae can be found here.
I find deserts always interesting, providing ample niche habitats for snails ‘living on the edge’. Whether these circumstances constitute ‘ecological stress’ leading to peculiar shell shapes or not remains an open question for me (as discussed in this post). Certainly it forms a ‘playground’ for genetical research.
References
Stuardo, J. & Valdovinos, C., 1985. A synonimic list of Chilean bulimulids (Mollusca: Pulmonata). - Boletin Sociedad Biologia Concepcion 56: 55-58.
Stuardo, J. & Vega, R., 1985. Synopsis of the land Mollusca of Chile, with remark on distributions. - Studies on Neotropical Fauna and Environment 20: 125-146.
Valdovinos, C. & Stuardo, J., 1988. Morfología, sistematica y distribución del género Plectostylus Beck, 1837 (Pulmonata: Bulimulidae). - Gayana, Zoologia 52: 115-195.
The latter publication is a synopsis of the land snails, for which detailed catalogues and group analyses were announced “to be published by parts elsewhere”. A far as I know, only a revision of Plectostylus appeared (Valdovinos & Stuardo, 1988).
As is also the case in other countries, the Orthalicidae are a major element of the Chilean terrestrial malacofauna. 42 taxa are listed, one doubtfully recorded for Chile (belonging to Thaumastus); the others all belong to Bostryx and Plectostylus.
While the latter genus has been largely revised, Bostryx remains quite ‘messy’ with 29 taxa. All species occur in northern Chile and seem to flourish in the desertic coastal area. An overview of the Chilean Orthalicidae can be found here.
I find deserts always interesting, providing ample niche habitats for snails ‘living on the edge’. Whether these circumstances constitute ‘ecological stress’ leading to peculiar shell shapes or not remains an open question for me (as discussed in this post). Certainly it forms a ‘playground’ for genetical research.
References
Stuardo, J. & Valdovinos, C., 1985. A synonimic list of Chilean bulimulids (Mollusca: Pulmonata). - Boletin Sociedad Biologia Concepcion 56: 55-58.
Stuardo, J. & Vega, R., 1985. Synopsis of the land Mollusca of Chile, with remark on distributions. - Studies on Neotropical Fauna and Environment 20: 125-146.
Valdovinos, C. & Stuardo, J., 1988. Morfología, sistematica y distribución del género Plectostylus Beck, 1837 (Pulmonata: Bulimulidae). - Gayana, Zoologia 52: 115-195.
More on Neotropical malacology
16-12-2008 19:33
Yesterday arrived the
Unitas Malacologica
newsletter,
with a report of the CLAMA VII congress in Chile.
More than 280 people from 16 countries attended.
In the report the “Latin American Association for
Malacology (ALM)” is mentioned. However, when I
tried to look it up with Google, I didn’t find any
result. It looks like a “phantom organisation”,
one that exists only virtually (?).
Anyway, I stumbled upon the website of the Sociedad Malacológica de Chile. They appear to have an annual newsletter too, Boletín Amici Molluscarum. In their latest issue (2007) I found a list of members: 57 + 5 members from abroad + 2 honory members. That is much more than the 9 listed in my previous post.
Each number of Amici Molluscorum (at least the more recent ones, but also some of the older) contain a few papers, predominantly on marine molluscs. For a country with such a huge shoreline it should not be a surprise.
In the announcements I saw a paper by one of the members on Pre-Colombian malacology. Also a book on the shell collection of the late Pablo Neruda was mentioned. Probably hard to get outside the country. But I’ll have a look for it, you never know.
Anyway, I stumbled upon the website of the Sociedad Malacológica de Chile. They appear to have an annual newsletter too, Boletín Amici Molluscarum. In their latest issue (2007) I found a list of members: 57 + 5 members from abroad + 2 honory members. That is much more than the 9 listed in my previous post.
Each number of Amici Molluscorum (at least the more recent ones, but also some of the older) contain a few papers, predominantly on marine molluscs. For a country with such a huge shoreline it should not be a surprise.
In the announcements I saw a paper by one of the members on Pre-Colombian malacology. Also a book on the shell collection of the late Pablo Neruda was mentioned. Probably hard to get outside the country. But I’ll have a look for it, you never know.
Carination revisited
10-12-2008 16:56
While searching some literature on Chile for a
friend, I found an interesting paper on the ecology
of a Bostryx species from the desert in the northern
part of the country. It also sheds some new light on
the phenomenon of carianation (subject of an upcoming
paper) and relates to the specialization / speciation
discussion briefly summarized
here
and
here.
In 1970, the paleontologist Herm described a new species, Bostryx variabilis, from Pleistocene marine sediments near Antofagasta.
Map showing the area just north of Antafagasta (from Herm, 1970)
To explain the occurrence of this terrestrial species amidst marine facies, he postulated a sea level regression-transgression. The species is carinated (keeled) and partially uncoiled.
In 1981, Alan Craig -a geographer- did field work in the same region and made some observations which questioned Herm’s hypothesis. He found many specimens of B. variabilis in nearby localitions, but they were restricted to places where also fossilized lichens occurred. Moreover he found transitions to a Recent species, B. mejillonensis (Pfeiffer, 1857).
Isotopic dating yielded an age of 2180 +/- 50 yr B.P., making the Pleistocene sea level change as postulated by Herm unnecessary for the type locality.
But how to explain the occurrence of B. mejillonensis-variabilis at this place? Eventually it appeared that Bostryx mejillonensis was only found in localities where meteorological circumstances sustained epiphytic colonies of lichens on cacti at the top of a hill nearby the type locality of Herm. At the slopes below the elevation where the seasonal fog banks have influence, the hyperarid desert constitutes a barrier for the dispersal of snails. The hill top thus forms an ecological island. This finally led Craig to hypothesize that B. mejillonensis had been forced outside their habitat into the surrounding desert from where they were unable to escape. Rapid changing environmental conditions would have ‘stress-induced’ a speciation process which led to the aberrant form of B. variabilis. Support for this hypothesis were field observations by Craig of runnels, caused by occasional winter rains, leading to downslope transportation of snails.
Area just north of Antafagasta with the localities mentioned by Herm (1970) and Craig (1985) indicated. The distribution area of lichens indicated by Craig marked on Morro Moreno in white (source: Google Earth).
Given the hypothesis briefly outlined above, my question is: is carination as observed in other places (e.g., here and here) also best explained as a ‘stress-induced speciation process’? If so, are there analogous ecological circumstances that force snails to transform into aberrant, carinated and -sometimes even - uncoiled shells?
References:
Craig, A.K., 1985. Speciation and age revision of the Atacaman snail Bostryx variabilis Herm. - Quarternary Research 23: 382-387.
Herm, D., 1970. Bostryx variabilis n.sp., eine Landschnecke aus dem Altpleistozän von Mejillones, Nordchile. - Mittheilungen Bayerischen Staatssammlung Paläontologie und historische Geologie 10: 189-198.
In 1970, the paleontologist Herm described a new species, Bostryx variabilis, from Pleistocene marine sediments near Antofagasta.
Map showing the area just north of Antafagasta (from Herm, 1970)
To explain the occurrence of this terrestrial species amidst marine facies, he postulated a sea level regression-transgression. The species is carinated (keeled) and partially uncoiled.
In 1981, Alan Craig -a geographer- did field work in the same region and made some observations which questioned Herm’s hypothesis. He found many specimens of B. variabilis in nearby localitions, but they were restricted to places where also fossilized lichens occurred. Moreover he found transitions to a Recent species, B. mejillonensis (Pfeiffer, 1857).
Isotopic dating yielded an age of 2180 +/- 50 yr B.P., making the Pleistocene sea level change as postulated by Herm unnecessary for the type locality.
But how to explain the occurrence of B. mejillonensis-variabilis at this place? Eventually it appeared that Bostryx mejillonensis was only found in localities where meteorological circumstances sustained epiphytic colonies of lichens on cacti at the top of a hill nearby the type locality of Herm. At the slopes below the elevation where the seasonal fog banks have influence, the hyperarid desert constitutes a barrier for the dispersal of snails. The hill top thus forms an ecological island. This finally led Craig to hypothesize that B. mejillonensis had been forced outside their habitat into the surrounding desert from where they were unable to escape. Rapid changing environmental conditions would have ‘stress-induced’ a speciation process which led to the aberrant form of B. variabilis. Support for this hypothesis were field observations by Craig of runnels, caused by occasional winter rains, leading to downslope transportation of snails.
Area just north of Antafagasta with the localities mentioned by Herm (1970) and Craig (1985) indicated. The distribution area of lichens indicated by Craig marked on Morro Moreno in white (source: Google Earth).
Given the hypothesis briefly outlined above, my question is: is carination as observed in other places (e.g., here and here) also best explained as a ‘stress-induced speciation process’? If so, are there analogous ecological circumstances that force snails to transform into aberrant, carinated and -sometimes even - uncoiled shells?
References:
Craig, A.K., 1985. Speciation and age revision of the Atacaman snail Bostryx variabilis Herm. - Quarternary Research 23: 382-387.
Herm, D., 1970. Bostryx variabilis n.sp., eine Landschnecke aus dem Altpleistozän von Mejillones, Nordchile. - Mittheilungen Bayerischen Staatssammlung Paläontologie und historische Geologie 10: 189-198.